The purpose of this work is to develop a new class of miniature precision acoustic sensors (hydrophones) which would survive in an in-vivo shock wave field. The immediate application of the device is in improving the safety and efficacy of Extracorporeal Shock Wave Lithotripsy (ESWL) treatment of kidney and gallbladder stones. The proposed research involves 1) theoretical modeling to examine design trade-offs associated with material choice and sensor configuration; 2) materials testing to determine acoustical properties and durability; 3) prototype design and assembly; 4) acoustical performance characterization; and 5) survivability tests under shock wave conditions. When fully developed under Phase II, the hydrophones would be used for in-vivo monitoring of ESWL treatment. The hydrophone will be small (<1mm diameter), wideband (>100MHz bandwidth), nearly omnidirectional (>90o capture angle), and robust enough to survive repeated shock waves. It will contribute to significant advances in lithotripsy treatment, in terms of understanding the mechanism of stone destruction and tissue damage, improving treatment efficacy, reducing patient trauma, and regulating new lithotripsy technology. Beyond lithotripsy applications, the hydrophone will be useful for in-vivo and in- vitro diagnostic ultrasound dosimetry, oceanography, and other applications requiring robust miniature acoustic sensors.